DNS servers translate the web address you type into your browser into the actual IP address of the internet server you're connecting to at the other end. Windows gets default servers from your ISP but they may not be high performance and they probably don't provide security filtering of bad websites. Switching over to a more secure DNS is free and very easy. It will help protect you from fraudulent websites that attempt to steal your personal information and money by blocking your visit to them. All you need to do is enter the OpenDNS addresses, 18.104.22.168 and 22.214.171.124, in Primary DNS Server and Secondary DNS Server fields on your router if you want to cover your whole network, or directly your machine if you prefer. The provided link gives you detailed instructions on how to do this for a machine or router.